1. Field of the Invention
The present invention relates to an apparatus and method for filling a silencer with a sound insulating material. More particularly, the present invention relates to an apparatus and method for filling a silencer with continuous texturized fibers which allow for a uniform filling of the silencer.
2. Description of the Related Art
The basic structure of silencers, such as mufflers used in automobiles, is well known in the art. A standard silencer or muffler includes one or more pipes which pass through a canister. The pipe is often perforated so that gas may pass from the interior of the pipe into the canister. The space between the pipe and the canister is filled with a sound insulating material which silences or muffles the noise caused by the air exhausted from the engine.
It is known in the art to fill a canister with glass fibers. The most commonly used conventional method of filling a silencer involves blowing glass fibers into the canister around the pipe. This type of method is shown in the patents to Ingemansson et al., U.S. Pat. No. 4,569,471, and Broadbelt et al., U.S. Pat. No. 4,774,985. Such a procedure is, however, imprecise. The blowing procedure does not produce mufflers which have a consistent density of fibers in all areas of the canister surrounding the pipe. In addition, the blowing procedure further limits the precision of the silencers made, in that the density of the fibers is not consistent between silencers produced using this process.
Some have attempted to solve this problem by wrapping glass fiber mats around the perforated pipe. This type of process is shown in the patents to Ikeda et al., U.S. Pat. No. 5,461,777, and Tamano et al., U.S. Pat. No. 5,479,706. This tends to correct the problem of the uniform density of the fibers. However, these mats are typically made from fibers which are short (1"-4"). The short length of these fibers leads to more rapid deterioration of the sound absorbing capacity of the silencer compared to using continuous fibers.
Still others have made preforms which are then placed within a canister. An example of this method is shown in European Patent Application No. EP 0692616 A1, by Knutsson. A drawback of this method is that a preform must be made for each type and size of muffler individually. In addition, the fibers are still blown into the preform mold, in a way similar to the Broadbelt and Ingemansson methods, which causes the same problems as mentioned above. Thus, the making of a preform does not solve the current problems in the silencer or muffler area.
What is needed instead is a method and apparatus which allows for uniform filling of a muffler to improve the sound-deadening abilities of the muffler in an economical manner. In addition, the needed method and apparatus must be able to function with continuous fibers in order to reduce the tendency of the insulation of silencers to deteriorate and the shorter fibers to separate from each other and blow out through the exhaust into the atmosphere. The present invention solves these and other problems currently in the art.